1. Field of Invention
The present invention is related to a calibration system and a method thereof for calibrating a display, and more specifically, to a calibration system and a method thereof for color calibration of a display.
2. Description of Related Art
In the recent years, the display technology has significantly developed. A significant portion of the traditional cathode ray tube (CRT) displays has been replaced by the panel displays. One of the most common panel displays is the thin-film transistor liquid crystal display (TFT-LCD). In addition, the plasma display and the organic light emitting diode (OLED) display become more and more common. The display part of the panel display includes the pixel array. The pixel array is an ordinary matrix array, and the pixel array is driven by a driver. The driver drives the corresponding pixels based on the arrayed image data. The pixels display the specific colors at the specific time under control by the driver. However, the color of the pixel is still required to be calibrated (such as gamma curve correction) in order to match the ideal color for the human eyes.
Please refer to FIG. 1, and FIG. 1 is a diagram showing the relationships between the gray level and two chromaticity values x and y of the CIE xyY color space of a conventional display panel. The vertical axis represents the two chromaticity values x and y, and the horizontal axis represents the gray level. In addition, the curve 260 responds to the chromaticity value x, and the curve 262 responds to the chromaticity value y. The two chromaticity values x and y are measured when the display panel displays patterns. Each of the patterns corresponds to a gray level, and the gray level is regarded as the graduation of the horizontal axis of FIG. 1. Each of the patterns may be a black pattern, a gray pattern, or a white pattern. For instance, the pattern corresponded to the gray level of 0 is a black pattern, the pattern corresponded to the gray level of 255 is a white pattern, and the pattern corresponded to the gray level of 1 to 254 is a gray pattern. In an ideal case, the two measured chromaticity values x and y may be constant. Otherwise, the color temperature corresponded to the gray levels is various. In other words, if the measured chromaticity values x and y are not constant, the color temperature of each of the gray levels is not fixed, such that display panel does not displays the color uniformly.
The Taiwan Patent No. 200306123, corresponding to the U.S. Pat. No. 7,079,155, provides an image display device, an image processing method, and a computer-readable medium adapted to perform proper color reproduction while saving memory capacity. The image display device uses a first color corrector to refer to a three-dimensional color correction table, matching a color characteristic of the image display device with a reference color characteristic based on a characteristic value of the image display device, and to apply desired color correction to the inputted image data. Then, the image display device uses second color corrector to refer to a one-dimensional color correction table for correcting gradation according to an application circumstances, and applies desired color correction to the inputted image data.
Another Taiwan Patent No. I283852, corresponding to the U.S. Pat. No. 7,375,854, discloses a method for color correction. A plurality of groups of gray levels and luminance of a light source of a display device are respectively selected by a color measurement system. The selected data of each color light are respectively calculated to obtain fitting functions, and the fitting functions may fit the gray level data of each interval. The fitting luminance of the gray levels in interval is obtained by the fitting functions and formed into a look-up table. Then in order to correspond a gamma curve of normalized gray data of image to a predetermined target curve, the two gamma curves are first taken to logarithmic calculation and the modified gray signals are obtained from the look-up table, then the modified gray signals are transmitted out for providing the display device to express the gray distribution state.